Shared Resources Laboratories (SRL) are fundamental cornerstones of the 2003 NIH Roadmap. Often referred to as core laboratories, SRLs are the most cost-effective approach to provide a broader range of scientific expertise from skilled technology scientists and advanced instrumentation than would be feasible or economically-viable for individual laboratories. Best practices for a Flow Cytometry SRL include: 1) stable and consistent financial support, 2) a qualified head of the core, 3) policies conducive to recruitment and retention of highly skilled technical staff, 4) user training and staff continuing education, 5) a quality control program for the instruments, 6) support for research and development, 6) overview of satellite facilities, and 7) at a minimum, a 5-year plan for future technology expansion and operation based on a seven-year life cycle for instrumentation. The NIA Flow Cytometry Unit (LMBI) functions as a Shared Resource Laboratory (SRL) to provide analytical flow cytometric analysis and cell sorting services to the entire NIA IRP. The core was judged to be exceptional in its last review. The core is used by investigators from every bench-science based laboratory in the Baltimore IRP. 99.5% of the core usage, facilities, and publications coming from the core are in support of NIA intramural scientists. Laboratory usage has increased over the years as sorting capacity has increased along with new research initiatives by IRP labs, such as sorting human and mouse immune cells, murine muscle stem cells and bone marrow stem cells. Sorting is heavily utilized by users that require multiple instruments (2-4) for the full day or greater in order to process in excess of 300 - 500 million cells. Some investigators experimental protocols require specific instruments. Besides the current core users, two additional laboratories have projected substantial sorting needs (50-100 sorts and >400 million cells for processing) in the near future, obligating full use of the sorting capacity for 5 days per week. Because of need for high volume sorting, the core has a 4th staff member who is responsible for extended hours sorting, nominal from the hours of 6PM to 4AM. The flow core is an integral part of long-term, longitudinal study (Gestalt) inter-laboratory examining changes blood cell subpopulations (T, B, monocyte) at the immunological, functional and epigenetic levels. This project, initiated by the SD, NIA IRP, utilizes a substantial portion of the core resources. The core is also involved in another long-term interlaboratory project specifically examining methylation and other epigenetic changes in rat immune cells over the natural lifespan of these animals. The core provides cutting edge, state-of-the-art flow cytometry for multi-parameter (polychromatic) analysis and sorting. Our core is unique with instrumentation from each major manufacturer. We have the only 7-laser MoFlo XDP high speed sorter and one of 9 iCyt Reflection HAPS (Highly Automated Parallel Sorting) instruments (1 of 2 of the 3 HAPS instruments in existence). It is housed in a Baker BL-2 hood for sorting adeno- and lentivirus-infected animal and human cells. Each HAPS is configured differently to provide the maximum flexibility for investigators experimental design. Our MoFlo is equipped with a Coherent Genesis MX 460nm and is the only instrument in a 50 mile radius able to perform chromosome analysis and sorting. It is also equipped with a Propel NanoView forward scatter detector, enabling detection and sorting of submicron particles in the down to 100nm, i.e exosomes. The laboratory space for the BRC facility was designed to house the Aria SORP (4 lasers) in a dedicated BL-3 room to be able to sort live non-human primate cells. In 2017, we added two high end flow cytometry analyzers: BD-Symphony (30 colors) and Beckman Coulter CytoFlex (26 color), which are greatly enhanced the ability to conduct high-dimensional flow cytometry analysis. The mission of the NIA flow cytometry shared resource lab is to enhance the scope and quality of the research within the IRP by providing all investigators with the expertise necessary to employ its advanced technologies optimally for their research. This includes having a qualified director and skilled staffs to actively consult on experimental design, implement, and interpret the results. The core also originates new procedures, suggests or performs the critical experiments that take their research in new directions, which advances technological developments in the field. Users can visit the core web page, in use since 1999 and operate some common instruments after through training and certification. The NIA Flow Cytometry Unit is organized and managed in a manner consistent with the policies and staffing levels of flow cytometry cores at extramural academic institutions and at NIH. Relevance to the NIA IRP Program In addition to the level of core utilization by investigators, measurement of the effectiveness and value of the core to IRP productivity is evident from the publications generated by NIA investigators using flow cytometry/sorting as an integral part of their research since the cores inception in 1999.